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  #21  
Old 04-17-2018, 08:19 AM
Aggie78 Aggie78 is offline
 
Join Date: May 2014
Location: New Braunfels, Texas
Posts: 450
Default Smoke Hoods

Smoke in the cockpit is one of my biggest concerns...I have had it happen before in a Transport Category aircraft (fire broke out behind engineer?s panel) and it filled the cockpit with smoke so fast I couldn?t believe it. Luckily, we were on the ground taxiing in, so we came to a screeching halt, killed power, and dumped the crew by doing the Evac checklist. Killing power killed the fire, but even then, it still smoked for a long time....if it had happened 15 minutes earlier in flight, I don?t like to wonder what the outcome could have been. Especially since we had just shot an approach at night, overwater, near minimums.

I carry that concern to the GA aircraft I fly. Airlines are required to provide a number of ?PBE? or Personal Breathing Devices to cockpit and crew in the event of a fire/smoke event. I decided to search the marketplace for something similar to at least give me a fighting chance of getting the aircraft on the ground before becoming overcome if I have another smoke event. I found a supplier that has these:

https://www.aeromedix.com/safety-equ...e60-smoke-hood

I bought a couple of them to fly with. While they aren?t TSO?d like the stuff in the Part 121 world, they don?t carry the $$$$ price tag those have either. All I?m wanting from them is 10-15 minutes to put the airplane down...somewhere. Anywhere.

Like I said, I?m looking for a fighting chance; having had a few smoke events now over 30+ years, I?m convinced that I won?t be able to hold my breath or keep my eyes clear without some kind of help. I hope I never use these things, but I?m glad I?ve at least got them with me...
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  #22  
Old 04-17-2018, 08:50 AM
Aluminum Aluminum is offline
 
Join Date: Jul 2017
Location: San Jose, CA
Posts: 326
Default

Quote:
Originally Posted by rv7charlie View Post
Dan V,
Is your battery mounted directly behind that switch? The reason for a master contactor is the ability to disconnect the fat wire *at the battery*. So if you can put that style switch within a few inches of the battery, it's a great solution. Many others have done the same.
Correct, the battery is about six inches away. Only the thick zero gauge cable going from it to the switch. The switch is rated to pass 1000 amps for half a minute. It will disconnect a short very reliably. Relays can fuse if disconnected under a high-current short.

I suppose the battery cable could still short in theory, but one has to draw the line somewhere. Also, it is my understanding that Odyssey and other motorcycle AGM batteries have internal fusible link designed in to prevent battery fire in case of a wrench-across-terminals event.
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'91 Zodiac 2013-2020 retired
RV-14A wiring
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  #23  
Old 04-17-2018, 09:03 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by Aluminum View Post
The standard master relay circuit design still baffles me. As in, who in their right mind could have come up with such a failure-prone design in the 1950s, and why does it endure. I did different on my first build, and will repeat on my second as I see no downside to what I did after five years of use.

Install a big mechanical master switch as the only thing the positive battery terminal connects to. Pass the starter current through the switch. Much safer and easier to debug. Esthetics can be improved I'm sure.

Not a cure all in my opinion.....

It is not practical to mount the battery close to the instrument panel (accessibility for maint., lower level of safety should something really bad happen with the battery, etc.).
That means adding a bunch of additional weight in heavy cable to do an out and back (and the added danger of heavy cable penetrating structure with no way to depower it, along with some additional structural penetrations that add potential problems, starter cranking amps losses, etc.

I agree that the master relay method does have a failure potential, but it is a rather rare failure.
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  #24  
Old 04-17-2018, 10:29 AM
vic syracuse vic syracuse is offline
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The switch posted in the prior post is not meant to be mounted in a panel. It is supposed to be mounted as close to the battery as possible.

Vic
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  #25  
Old 04-17-2018, 01:05 PM
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Phil Phil is offline
 
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Location: Waco, Texas
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I did this on my RV-10 (aft battery configuration) with the Light Speed power wire. Coming off the battery there is a 15 amp in-line fuse. Then it goes on forward to a panel mounted 7.5 amp circuit breaker.

The theory is that a malfunction of the LSE box would pop the CB prior to the fuse blowing. Thus, enabling me reset it in flight if I absolutely had to do it. Or even giving me the opportunity to reboot it inflight if I suspect it could be acting flakey.

But if there was a dead short somewhere between the tailcone mounted battery and the panel mounted CB, then the 15 amp fuse will blow fairly quickly and open the line before much smoke is released.

Quote:
Originally Posted by az_gila View Post
I agree on the fuse bit, and just had to go and read the LSE manual.

To connect power to the ignition system, install the 15-pin input connector from your sensor harness to the ignition module. Route the single conductor shielded power lead to a pull-able breaker, 4-cyl systems use 5A and 6-cyl systems use 7.5A, and then directly to the battery plus terminal, bypassing any electrical buss or master solenoid. Refer to the Input Connector Diagram & the Electrical Requirements.

If I was installing one I think I would add a fusible link at the battery in the breaker-to-battery wire connection.
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  #26  
Old 04-17-2018, 01:54 PM
Aluminum Aluminum is offline
 
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Quote:
Originally Posted by vic syracuse View Post
The switch posted in the prior post is not meant to be mounted in a panel. It is supposed to be mounted as close to the battery as possible.

Vic
Correct, the battery is next to the switch in this install. For behind-the-seat batteries the switch could be recessed between the seats.
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'91 Zodiac 2013-2020 retired
RV-14A wiring
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  #27  
Old 04-17-2018, 02:00 PM
Aluminum Aluminum is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Not a cure all in my opinion.....
Agreed, nothing cures all, even staying on the couch.

Quote:
Originally Posted by rvbuilder2002 View Post
I agree that the master relay method does have a failure potential, but it is a rather rare failure.
My configuration also solves the fused-starter-relay situation, which is fairly common as that contact breaks a couple of hundred amps after every engine start.
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'91 Zodiac 2013-2020 retired
RV-14A wiring
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  #28  
Old 04-17-2018, 02:32 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Aluminum View Post
Agreed, nothing cures all, even staying on the couch.



My configuration also solves the fused-starter-relay situation, which is fairly common as that contact breaks a couple of hundred amps after every engine start.
Problems are based on personal opinions I guess......

I wont say it doesn't happen, but saying that a stuck starter relay is a reason to have a manual switch is not a good reason in my opinion.
From my experience it would be more appropriate to say it is fairly rare... not fairly common, and in the rare occurrence, if a traditional master relay has been utilized, it would remove power from the starter just as well.

If you used a manual switch and are happy with it... great. That's why they call them experimental.
Just adding another perspective for those still brainalizing their electrical system.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
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Van's Aircraft Engineering Prototype Shop
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  #29  
Old 04-17-2018, 03:44 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Default

Quote:
Originally Posted by Phil View Post
I did this on my RV-10 (aft battery configuration) with the Light Speed power wire. Coming off the battery there is a 15 amp in-line fuse. Then it goes on forward to a panel mounted 7.5 amp circuit breaker.

The theory is that a malfunction of the LSE box would pop the CB prior to the fuse blowing. Thus, enabling me reset it in flight if I absolutely had to do it. Or even giving me the opportunity to reboot it inflight if I suspect it could be acting flakey.

But if there was a dead short somewhere between the tailcone mounted battery and the panel mounted CB, then the 15 amp fuse will blow fairly quickly and open the line before much smoke is released.
Phil,

Have you tested it for the action you desire? The reason I ask is that the time constant for most CBs is so much longer than a fast blow fuse, the fuse might well blow first under a lot of overload conditions.
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  #30  
Old 04-17-2018, 07:54 PM
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Rick_A Rick_A is offline
 
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Location: Jacksonville, FL
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I got to our hanger not long after the smoke event occurred and saw the damage. It's was an eye opener.

I've been thinking about my wiring and decided to add an in-line fuse from the aux battery (4Ah EarthX) that is mounted on my firewall. Even though I have a fuse in the cabin, there is probably 2 feet of unprotected wire between the battery and the fuse.

I'm going to add another fuse forward of the firewall just a few inches away from the battery terminal.
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